The known methods of reduction of pressure of gas in boreholes or in main pipelines are based on throttling and using special devices (pressure regulators, valves, cocks etc) for implementation of these methods. [Polytechnic Dictionary, Moscow, “Sovetskaya Entsiklopedia” Publishing House, 1977, pp. 153, 420]
These methods and devices for implementation thereof do not utilize energy of gas expansion and cold generated during this process. The application of these methods and devices requires sophisticated equipment and consumption of additional power to prevent clogging of pressure regulators by moisture and ice generated during their operation.
A method of utilization of energy of natural gas when its pressure drops from the value in the main pipeline or in the borehole down to the required pressure by conversion of gas expansion energy to mechanical energy is known. [RU 2117173, MΠK 6 F 02 C 1/02, 1996]. This method is implemented in a utilization power installation the inlet of which is connected to the outlet of the high pressure gas borehole or the main pipeline and the outlet—to the low pressure gas pipeline or to the gas consumer. This utilization power installation includes a gas expansion machine, e.g. an expansion turbine, and a mechanical energy converter connected kinematically with the gas expansion machine, e.g. an electric generator. Such method and the installation make it possible to utilize gas expansion energy when its pressure drops.
However this method and the installation do not provide the possibility of utilization of: cold generated in the process of gas expansion. The efficiency of this method and the installation is low.
There is a method of utilization of gas expansion energy when the gas pressure drops from a high value to the required one by conversion of gas expansion energy to mechanical energy with simultaneous utilization of the gas cooled down during pressure drop as a cooling agent for generation of cold. [SU, A1, 844797]
However this method provides a single-stage gas pressure drop and hence total efficiency thereof is reduced.
There is a power installation for utilization of gas expansion energy and the cold generated during this process. [RU 2013616, MΠK F 02 C 6/00, 1994]
However efficiency of this installation is low as gas pressure reduction and utilization of cold are effected at a single stage.